Field and laboratory studies directed toward evaluating the effectiveness of rubella vaccines and searching for more immunogenic ones will be continued. Follow-up serologic surveillance of vaccinated populations (2 and 5 years after vaccine administration) include tests for persistence of various types of antibodies, and evidence of reinfections. "Natural" immunes are being followed similarly for comparison. Laboratory investigations will be directed toward analysis of immune responses to purified antigens derived from the nucleocapsid and envelope fractions of the virus, including anti-theta and anti-iota. Wild and vaccine strains will be compared, with special attention to RA 27/3 which appears to more closely resemble wild virus in its immunogenicity than do the other vaccine strains.